Steering gear

ABSTRACT

Rack and pinion steering gear with fluid damping to absorb undesirable feedback from the rack bar to the steering column. The damping may be controlled from a maximum in the median or straight-ahead steering range to a minimum as the two extremities of the steering range are approached.

United States Patent Inventor Appir N0. Fi1ed Patented Assignee PrioritySTEERING GEAR 12 Claims, 4 Drawing Figs.

US. Cl 74/498,

74/422 Int. CL; 862d 3/12 Field of Search 74/498,

[56] References Cited UNITED STATES PATENTS 806,684 12/1905 Lemp 74/498X 833,230 10/1906 Lemp 1 74/498 1,135,923 4/1915 Reynolds 188/88.5021,574,601 2/1926 Brundage 188/91 1,701,007 2/1929 Libani 188/912,913,919 11/1959 Malkiewicz 74/422 X 3,347,109 10/1967 Adams et a1.74/422 X FOREIGN PATENTS 946,501 1/1964 Great Britain 74/498 PrimaryExaminer-Carlton R. Croyie Assistant Examiner-Thomas C. PerryAtt0rney-Hill, Sherman, Meroni, Gross and Simpson ABSTRACT: Rack andpinion steering gear with fluid damping to absorb undesirable feedbackfrom the rack bar to the steering column. The damping may be controlledfrom a maximum in the median or straight-ahead steering range to aminimum as the two extremities of the steering range are approached.

PATENTEDJuL20l9n 3.593592 SHEET 1 BF 2 INVENTOR F DERICK JOHN ADAMSATTORNEYS PATENTEDJULZOIS?! SHEET 2 OF 2 INVENTOR ATTORNEYS FREDERICKJOHN ADAMS STEERING GEAR BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to the steering gear art, andparticularly to rack and pinion steering, and provides damping means toabsorb objectionable or excessive feedback to the steering column. Theinvention aims to limit the velocity at which unda'mped feedback forceswould be effective to rotate the steering column and in a specificembodiment controls the damping rate from a maximum in thestraight-ahead position to a minimum at the extreme turned positions.

SUMMARY OF THE INVENTION This invention now minimizes driver fatigue bydamping out feedback forces to the steering column in rack and pinionsteering gear. The damping is accomplished by controlling liquid flowbetween two chambers surrounding the rack bar of the steering gear. Therack bar has piston or plunger means movable therewith to displace theliquid from one to the other chamber. A restricted passage controls theflow between the two chambers. A reservoir for liquid is provided and isconnected to the two chambers through one-way valve means which supplymakeup liquid to the chambers but prevent back-flow of the liquid fromthe chambers to the reservoir.

The damping rate may be arranged so as to vary with the momentaryposition of the steering gear. For example, it may be desirable toprovide for maximum damping in the median steering range which is in arange ofthe total "lock" (extreme left to extreme right) whichcorresponds nearly to straight wheel" or neutral steering, withdiminishing damping as the two extremities of the range are approached.When steering at a near maximum lock position (extreme right or left), adriver is not likely to be upset by a steering wheel reaction orfeedback because he must in the very nature of driving be proceedingslowly in such extreme steering positions. It will be understood,however, that the present invention is hot dependent upon the provisionof graduated damping, but is concerned with damping in rack and pinionsteering which inay be economically and simply provided and which hasits own topping up" in the event ofloss ofliquid, and which may alsohave externally accessible adjustment of damping.

It is then an object of this invention to provide damping means for rackand pinion vehicle steering gear which will absorb objectionablefeedback to the steering column.

Another object of the invention is to provide rack and pinion steeringgear with opposed liquid chambers surrounding the rack bar and meanscontrolling flow of liquid between said chambers, together with pistonmeans movable with the rack bar in said chambers to displace liquid fromone chamber to the other as the rack bar is shifted.

Another object of this invention is to provide a liquid dampener forrack and pinion steering.

Another object of this invention is to provide a rack and pinion vehiclesteering gear which will damp out feedback forces from the steeringwheels to the steering column in a controlled manner with a maximumeffect in the straightahead position diminishing to a minimum effect inthe extreme steering positions.

A specific object of this invention is to provide a rack and pinionsteering gear with a rack bar slidable through a housing and carryingpistons sealing against the housing which displace liquid through adamping passage as the rack bar is shifted, thereby minimizing feedbackforces to the steering column.

Other and further objects of this invention will be apparent to thoseskilled in thisart from the following description of the annexed sheetsof drawings which, by way of preferred examples only, illustrate severalembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinalcross-sectional view of a rack and pinion assembly according to thisinvention and having an integral liquid reservoir;

FIG. 2 is a view similar to FIG. 1 showing an alternate arrangementwhere the liquid reservoir is remotely located, and also illustrating indotted line an externally accessible damping passage;

FIG. 2a is a fragmentary longitudinal cross-sectional view showing afurther alternate arrangement functionally resembling the arrangement ofFIG. I, but only having one piston and two seals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. I is seen a rackbar l,sliding iin a cylindrical housing 2 and operated by the rack and pinionmechanism shown generally at 3. The cylindrical housing .2 has fixed init an annular seal at 4 through which slides the bar I. On the bar I aremounted two piston elements 5, 6, which slide operable in the housing 2;the piston 5 and seal 4 enclose a pressure chamber 7, and piston 6 andseal 4 enclose a chamber8. On the housing 2 is carried a chamber 9 forliquid. This communicates with the chambers 7 and 8, by nonreturn ballvalves 10, ll, of which the balls are preferably buoyant so that theytend to assume a closed position. Through the seal 4 is provided adamping passage 12 which controls the leakage of liquid between thechambers 7 and 8. The valves 10, II ensure that the chambers are keptfull of liquid from the reservoir 9. When the bar I is moved (forexample) from left to right, liquid is displaced from chamber 7 intochamber 8 through the passage 12, which passage damps the flow accordingto its rate. Sudden movements are thereby checked.

In FIG. 2 the rack bar 20 is actuated by the rack and pinion indicatedat 21, and it slides within the cylindrical housing 22. In this is fixeda seal 23 in the form of a bush fixed in the casing and having a slidingclearance at 23A forming the damping passage. The bar 20 has fixed on ittwo unidirectionally operable pistons 24, 25, which with the seal 23define annular pressure spaces 26, 27. On the outer sides of the pistons24, 25 and between them and the ends of the bar are chambers 28, 29which are closed at the remote ends of the housing 22 by flexiblebellows 30 in known manner. The chambers 28, 29, which are to containnegligible pressure, are kept supplied with liquid from a reservoir 31by pipes 31A, 318. Thus, any deficiency of liquid in chambers 27, 28 ismade good from the reservoir by liquid unidirectionally passing thepistons: the pistons in this function, act like nonreturn valves.

Referring also to FIG. 2, there are illustrated at 238 in dotted lines,longitudinal channels or grooves in the rack bar progressivelyincreasing cross-sectional area downstream from each side of the centralor straight-ahead steering position of the rack bar. In this arrangementmaximum damping is provided when the steering is near neutral orstraight-ahead," and the damping increases with increasing displacementof the rack bar toward end lock positions.

In FIG. 2A an alternate form of seal or damping passage is illustrated.As shown, the cylinder 22 has fixed in it an annular element 30 with anelastic spring ring or retainer 30A retaining a bushing element 31 whichhas a clearance fit on the rack bar 20 and in the annular element 30.The total clearance is selected to provide the damping passage. Thisarrangement allows for misalignment of the rack bar in. the cylindricalhousing 22.

In FIG. 2 a further damping passage arrangement is shown in brokenlines. As there shown, the seal between the two chambers 26 and 27 isassumed to have a close fit on the rack bar 20, allowing little or noleakage therethrough (i.e., the clearance at 23A will not be present).Externally there is connected to the chambers 26 and 27 a bypass pipe 29interconnecting the chambers. A readily accessible adjusting screw 29Ais provided in this bypass pipe 29 to control flow therethrough and thusregulate the damping, The damping orifice controlled by the adjustingscrew 29A could, it'desired, be controlled by fluid pressure derivedfrom or related to an actuating pressure of a power-assisted steeringsystem.

In FIG. 3, the bar of FIG. 2 carries only one double-acting piston 40,sliding in the cylinder 22 between two unidirectional annular seals 41,42 which are fixed in the cylinder. The piston 40, and seals 41, 42enclose pressure chambers 43, 44, which have the same functions as 27,28 in FIG, 2'. The piston 40 is a clearance at 40A fit in the cylinder22, thus providing the damping passage.

Relief valving means may be provided to avoid excessive pressures in thechambers. This may be achieved by using a spring-loaded two-way valve,arranged to follow a selected valve law, as the damping orifice, so thatrelieved fluid either crosses to the lower pressure chamber or goes tothe reservoir.

From the above descriptions it will, therefore, be understood that thisinvention now limits feedback forces from rack and pinion steering gearto the steering column to relieve driver fatigue without, however,losing steering feel" or impeding steering action.

lclaim:

1. In a rack and pinion vehicle steering gear including a rack barhaving a rack, a pinion meshed with the rack for longitudinally shiftingthe rack bar and a housing surrounding the rack bar, the improvement ofmeans for damping feedback forces from the rack bar to the pinionincluding opposed pressure chambers in the housing surrounding the rackbar, piston means moving with the rack bar to displace liquid betweenthe chambers, and a damping passage connecting the chambers forcontrolling liquid flow therebetween.

2. The rack and pinion gear of claim 1 including a liquid reservoirconnected to each chamber for maintaining liquid in the chambers.

3. The rack and pinion steering gear ofelaim 2 in which the reservoir isconnected to each chamber through a. one-way valve.

4. The rack and pinion steering gear of claim 2 in which the reservoiris connected to each chamber by a one-way passage throughunidirectionally operating pistons on the rack bar.

5. The rack and pinion steering gear of claim 1 including a reservoirfor liquid mounted on the housing and connected to the pressure chambersthrough one-way valves.

6. A rack and pinion vehicle steering gear assembly comprising a tubularhousing, a rack bar slidable through said housing, longitudinally spacedpistons secured on said rack bar sealingly engaging said housing andproviding a sealed chamber therebetween surrounding the rack bar, sealmeans dividing said chamber into two compartments and having a dampingpassage connecting the compartments, means for maintaining said chamberfilled with liquid, and a pinion shifting said rack bar in said housingto displace liquid from one compartment to the other through saidpassage whereby feed back forces on the rack bar to the pinion will bedamped.

7. The rack and pinion gear of claim 6 wherein the seal means is fixedto the housing and has a passageway therethrough.

8. The rack and pinion gear of claim 6 wherein the seal means is fixedto the rack bar and the pistons are fixed to the housing.

9. The rack and pinion gear of claim 1 including means on the rack bareffective to vary the size of the damping passage 7 as the rack bar isshifted to vary the damping rate.

10. The steering gear of claim 1 wherein the clamping passage is in abypass duct external to the housing and has an externally accessiblecontrol for adjusting the size of the passage. 1

11. The rack and pinion gear of claim I wherein the rack bar has groovesof increasing cross-sectional area extending from opposite sides of thedamping passa e to increase the damping passage as the rack bar isshlfte towards the ex tremities of its operating positions.

12. The steering gear of claim 1 wherein the damping passage includes amovable bushing accommodating misalignment of the rack bar and housingwithout substantially affecting the damping action.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 592Dated July 20, 1971 FREDERICK JOHN ADAMS Inventor(s) It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 2, lines 15-18, cancel "FIG. 2a is a fragmentary longitudinalcross-sectional view showing a further alternate arrangementfunctionally resembling the arrangement of FIG. 1, but only having onepiston and two seals." and insert:

Figure 2a is a fragmentary longitudinal cross-sectional view showing analternate form of damping means for the assembly;

Figure 3 is a fragmentary longitudinal cross-sectional view showing afurther alternate arrangement functionally resembling the arrangement ofFigure l, but only having one piston and two seals.

Column 2, line 57, cancel "or" and insert -of.

Signed and sealed this 22nd day of February 1972.

(SEAL) Attest:

EDWARD M.FLEICHEH,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PC3-1050 (10-69} I USCOMM-DC BOS'IG-PBQ 9 U5 GOVERNMENTPRINTING OFFICE |9690366 33A

1. In a rack and pinion vehicle steering gear including a rack barhaving a rack, a pinion meshed with the rack for longitudinally shiftingthe rack bar and a housing surrounding the rack bar, the improvement ofmeans for damping feedback forces from the rack bar to the pinionincluding opposed pressure chambers in the housing surrounding the rackbar, piston means moving with the rack bar to displace liquid betweenthe chambers, and a damping passage connecting the chambers forcontrolling liquid flow therebetween.
 2. The rack and pinion gear ofclaim 1 including a liquid reservoir connected to each chamber formaintaining liquid in the chambers.
 3. The rack and pinion steering gearof claim 2 in which the reservoir is connected to each chamber through aone-way valve.
 4. The rack and pinion steering gear of claim 2 in whichthe reservoir is connected to each chamber by a one-way passage throughunidirectionally operating pistons on the rack bar.
 5. The rack andpinion steering gear of claim 1 including a reservoir for liquid mountedon the housing and connected to the pressure chambers through one-wayvalves.
 6. A rack and pinion vehicle steering gear assembly comprising atubular housing, a rack bar slidable through said housing,longitudinally spaced pistons secured on said rack bar sealinglyengaging said housing and providing a sealed chamber therebetweensurrounding the rack bar, seal means dividing said chamber into twocOmpartments and having a damping passage connecting the compartments,means for maintaining said chamber filled with liquid, and a pinionshifting said rack bar in said housing to displace liquid from onecompartment to the other through said passage whereby feedback forces onthe rack bar to the pinion will be damped.
 7. The rack and pinion gearof claim 6 wherein the seal means is fixed to the housing and has apassageway therethrough.
 8. The rack and pinion gear of claim 6 whereinthe seal means is fixed to the rack bar and the pistons are fixed to thehousing.
 9. The rack and pinion gear of claim 1 including means on therack bar effective to vary the size of the damping passage as the rackbar is shifted to vary the damping rate.
 10. The steering gear of claim1 wherein the damping passage is in a bypass duct external to thehousing and has an externally accessible control for adjusting the sizeof the passage.
 11. The rack and pinion gear of claim 1 wherein the rackbar has grooves of increasing cross-sectional area extending fromopposite sides of the damping passage to increase the damping passage asthe rack bar is shifted towards the extremities of its operatingpositions.
 12. The steering gear of claim 1 wherein the damping passageincludes a movable bushing accommodating misalignment of the rack barand housing without substantially affecting the damping action.